#include <stdio.h>

#define N 10000

int
main() {
	int i,p,q,t,id[N];
	for(i = 0; i < N; i ++) {
		id[i]	= i;
	} 
	while(scanf("%d %d\n",&p, &q) == 2) {
		if (id[p] == id[q]) {
			continue;
		}
		for (t = id[p],i = 0; i < N; i ++) {
			if (id[i] == t) {
				id[i]	= id[q];
			}
		}
		printf("%d %d\n", p, q);
	}
}